Ace Test series: Databases - Relational Algebra

Question

The solution says that it should return 50 tuples. But I think it should be 10 as the selection query is on the relational algebra.

Please need your help to clear this confusion. Thanks in advance.

Answer 1

it will be 50, in the question it is mention that the "the attribute value is uniformly distributed",

there are hundred tuples and there are 20 elements in set 100/20 = 5, i.e., for each attribute value there are 5 rows.

not less than 10 means 9*5 = 45, but it is given less than and equal to, 10*5 = 50. BTW which is equal for (>10) too.

Comments

but select in relational algebra doesnot return duplicate....

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million dollar comment, but applies only when relation has only $one$ attribute $A$

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Can you explain I’m not getting your point? @Debapaul

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uniformly distributed at intervals  [1-20] means

1-20  (from here we get 10 numbers given condition <=10) 

21-40

41-60

61-80

81-100

As you said, but select in relational algebra doesn't return duplicate...

No duplicate values are returned. 

@ priyanka manwani